code: def test_exponential_func():
      n_classes = 2
      result1 = exponential_func(n_classes, np.array([0.2]))
      assert result1 < 0.0
  
      result2 = exponential_func(n_classes, np.array([0.8]))
      assert result2 > 0.0
  
      assert result2 > result1
  
      result3 = exponential_func(n_classes, np.array([1.0]))
      result4 = exponential_func(n_classes, np.array([0.9]))
      assert result3 > result4 > result2 > result1
  
file_path: DESlib/deslib/tests/util/test_prob_functions.py
imports: import numpy
  import pytest
  from deslib.util.prob_functions import ccprmod, log_func, min_difference, softmax, exponential_func, entropy_func
label_desc: Use image node_id 13 for calling a global function with example usage: test_exponential_func() without return types